Evolution of directly-spinnable carbon nanotube growth by recycling analysis

Carbon nanotubes (CNTs) grown on substrate-bound catalysts by CVD are influenced by the catalyst, which changes over the course of the process. The evolution of the CNT growth is revealed by breaking the process into recycling increments and using the phenomenon of ‘direct spinnability’ as a target characteristic.Using acetylene alone, it was found that the first four cycles gave 100% regrowth in height and mass yield of CNTs, with both properties falling to around 20% on the 5th cycle. A decrease in nanotube diameter was observed whilst the areal density increased. With the addition of hydrogen a 100% regrowth for the second cycle was observed, followed by a decrease to around 55%, 18% and 11% in both height and yield for subsequent cycles. The diameter increased, whilst the areal density decreased in subsequent cycles.In the absence of hydrogen the CNTs have around seven walls, decreasing to about three by the seventh cycle. With hydrogen, CNTs have five or six walls for all cycles. Raman spectroscopy indicates an increase in disorder in later cycles. Spinnability is high for initial cycles but drops sharply on the fourth cycle, or third cycle with hydrogen, as the nanotube forest tortuosity markedly increases.     

Surface characteristics and electrochemical capacitances of carbon aerogels obtained from resorcinol and pyrocatechol using boric and oxalic acids as polymerization catalysts

Carbon aerogels were prepared by carbonizing (at 500–1500 °C) organic aerogels obtained from the polymerization reaction of resorcinol and/or pyrocatechol with formaldehyde using boric and oxalic acids as polymerization catalysts. Prepared samples were characterized by different techniques to ascertain their composition, surface chemistry, morphology, and surface physics, determining their electrochemical capacitances in acidic medium. The use of pyrocatechol yielded carbon aerogels that were micro–mesoporous, showing Type IV N₂ adsorption isotherms with Type H2 hysteresis cycles. The volume and size of mesopores depended on the acid catalyst used and the temperature at which the carbon aerogel was obtained. Conversely, the sample prepared with resorcinol and boric acid as catalyst was micro–macroporous and that obtained with a resorcinol–pyrocatechol mixture was micro–mesoporous but with large mesopores. Most of the boric acid used was lost during the exchange of water with acetone in the organic hydrogels before their supercritical CO₂ drying. Carbon aerogels obtained at 900 °C and using boric acid as polymerization catalyst showed a capacitance between 17 and 24 μF/cm². Boron influenced the capacitance because it increased the oxygen content. Sample synthesized using pyrocatechol, formaldehyde, and oxalic acid and heat-treated at 900 °C had the highest capacitance, 34 μF/cm².     

A process for the production of a diacylglycerol‐based milk fat analogue

We propose a novel process for the production of a DAG‐rich acylglycerol mixture derived from milk fat. This product has potentially interesting nutritional properties, derived from both its high content of DAG and of short‐chain fatty acids (FAs). The proposed process consists of three steps: lipase‐catalysed partial ethanolysis of milk fat, extraction of the by‐product fatty acid ethyl esters (FAEEs) using supercritical carbon dioxide (SC‐CO₂) and isomerization of DAG to increase the proportion of 1,3‐DAG. The experimental investigation of the process steps was done using milk fat and trilaurin. Several lipases were tested for maximizing the percentage of DAG in the acylglycerol mixture produced by ethanolysis. The selectivity of the chosen lipase was such that the produced AG mixture was enriched in short‐chain FAs in relation to the original milk fat. FAEEs were completely extracted from the ethanolysis mixture by SC‐CO₂. In the final process step, we explored the reaction conditions for facilitating acyl migration in the DAG mixture, so that the equilibrium proportion of 1,3‐DAG (～64%) was attained. Our results set the basis for the development of a simple process for the production of a DAG‐rich milk fat analogue.     

Phosphorus‐containing soybean‐oil copolymers: Cross‐metathesis of fatty acid derivatives as an alternative to phosphorus‐containing reactive flame retardants

Two different approaches to the creation of phosphorus‐containing soybean‐oil copolymers were investigated. First, two phosphorus‐containing styrene (ST) derivatives, diphenyl styryl phosphine oxide and dimethyl‐p‐vinylbenzylphosphonate (STP2), where tested as comonomers in the cationic copolymerization of soybean oil (SOY), ST, and divinylbenzene (DVB), to obtain heterogeneous systems in all cases. To overcome this drawback, the cross‐metathesis reaction of methyl 10‐undecenoate and STP2 was carried out to link the phosphorus moiety to the vegetable‐oil derivative. This second approach permitted the synthesis of a new reactive phosphorus‐containing plant‐oil derivative, which was incorporated into the soybean oil, ST, and DVB system. The cationic copolymerization was investigated, and the structure, thermal stability, and mechanical and flame‐retardant properties of the resulting copolymers were studied. Thermosets with moderate glass‐transition temperatures were obtained; this showed that the cross‐metathesis reaction is a convenient way to produce oil‐compatible monomers able to undergo homogeneous polymerization reactions. The resulting thermosets with 1% phosphorus had limiting oxygen index values about 24.0; this indicated an improvement in the fire‐retardant properties of the soybean‐oil‐based copolymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Development of monolithic porous composites using carbonized coals as block porous supports, and poly(furfuryl alcohol) and chitosan as fillers

In this study, monolithic block cokes have been used as supports to develop carbon–carbon and carbon–polymer monolithic block composites using poly(furfuryl alcohol) and chitosan as fillers. Cokes were produced from single coals and coal blends by carbonization at 950 °C. The supports and the resultant composites were characterized by means of elemental analysis (carbon, hydrogen and nitrogen—CHN), low-temperature physical adsorption of nitrogen, gas helium densitometry, electric and ultrasonic measurements. Morphology of the supports and the composites was observed using scanning electronic microscope. The supports were found to be porous carbon materials of high C content within the range of 97.6–98.5 wt%, of porous structure characterized by macropores, with low contribution of mesopores with diameters of 17–25 nm. The resultant composites were found to be porous light materials with apparent density of less than 1 g/cm³, and bulk porosity ranging from 35 to 54 %, with high stiffness evidenced by dynamic elastic moduli reaching values up to ~5 GPa. Addition of the polymers to the cokes (block supports) was found to worsen electrical properties giving the electrical conductivity values ranging from 0.2 to 0.5 S/cm for all composites studied.     

Oxygen Storage Behavior of Ceria–Zirconia-Based Catalysts in the Presence of SO2

This paper investigates the effect of the presence of SO₂ in the dynamics of oxygen storage on ceria and ceria–zirconia. The introduction of SO₂ under reaction conditions at T<873 K negatively affects CO conversion under oscillating conditions on all the supports studied, owing to the formation of sulfate species. Deactivation is observed on all supports and activity is recovered only after desorption of SO₂, which occurs at 950<T<1000 K, depending on catalyst composition (Ce/Zr ratio) and treatment atmosphere. The amount of sulfur adsorbed is higher over solid solutions, reaching a maximum with Ce _x Zr_1–x O₂ (0.5<x<0.68). However this does not adversely affect activity compared to ceria. In the presence of Rh and Pd, reactivation is favored under reaction conditions. More generally, it appears that the removal of sulfates is facilitated in reductive atmospheres (both hydrogen and CO) over mixed oxides. No differences are observed following regeneration under oxidizing conditions.     

Cr(VI) removal from synthetic and real wastewaters: The use of the invasive biomass Sargassum muticum in batch and column experiments

The macroalgae Sargassum muticum was selected for the treatment of solutions containing Cr(VI). Very acidic pH values were established as optimal for Cr(VI) reduction. Algae chemical modification reduced equilibrium time to 4 h. First order kinetic model was used to describe the reduction kinetic of Cr(VI). A column experiment allowed to distinguish the processes occurring during Cr(VI) elimination: its reduction to Cr(III) and the subsequent adsorption of this species formed. Under the selected conditions the biomass was capable of reducing all the incoming Cr(VI) during 77 h. Industrial wastewaters from chrome plating industry were also tested for chromium removal.     

Selective separation of yttrium from rare earth elements by ion interaction chromatography. Analytical and larger scale applications

ABSTRACT

New ion interaction chromatographic (IIC) method employing Kromasil 100 C₁₈ column and tetra-n-butylammonium hydroxide (TBAOH) as an ion interaction reagent (IIR) is able to separate yttrium from Rare Earth Elements (REE) as anionic complexes with nitrilotriacetic acid (NTA). New method for the chromatographic determination of Y in REE mixture was devised and validated by the analysis of the certified reference material (CRM). Potential possibilities of the new chromatographic system for larger scale applications including macro-micro events were demonstrated.     

Interleukin-1β Modulation of the Mechanobiology of Primary Human Pulmonary Fibroblasts: Potential Implications in Lung Repair

Pro-inflammatory cytokines like interleukin-1β (IL-1β) are upregulated during early responses to tissue damage and are expected to transiently compromise the mechanical microenvironment. Fibroblasts are key regulators of tissue mechanics in the lungs and other organs. However, the effects of IL-1β on fibroblast mechanics and functions remain unclear. Here we treated human pulmonary fibroblasts from control donors with IL-1β and used Atomic Force Microscopy to unveil that IL-1β significantly reduces the stiffness of fibroblasts concomitantly with a downregulation of filamentous actin (F-actin) and alpha-smooth muscle (α-SMA). Likewise, COL1A1 mRNA was reduced, whereas that of collagenases MMP1 and MMP2 were upregulated, favoring a reduction of type-I collagen. These mechanobiology changes were functionally associated with reduced proliferation and enhanced migration upon IL-1β stimulation, which could facilitate lung repair by drawing fibroblasts to sites of tissue damage. Our observations reveal that IL-1β may reduce local tissue rigidity by acting both intracellularly and extracellularly through the downregulation of fibroblast contractility and type I collagen deposition, respectively. These IL-1β-dependent mechanical effects may enhance lung repair further by locally increasing pulmonary tissue compliance to preserve normal lung distension and function. Moreover, our results support that IL-1β provides innate anti-fibrotic protection that may be relevant during the early stages of lung repair.